“Yes ... excruciating, and I can't straighten it all the way either,” Upson said.

At 54, she was told she needed a new right knee. Her kneecap didn't line up for a long time, a doctor told her.

That didn't surprise her. But she was surprised when her doctor, Steven Haas, M.D., of Hospital for Special Surgery, told her he would give her a high-performance kind of knee that moves and feels more like a natural one. It's especially good for women, he said, who require new knees more often than men because theirs are less muscular and more prone to injuries.

As compared to standard replacements, this new knee is narrower around the kneecap. Made of special ceramic, it's designed to be easier to bend and rotate.

It seems to make more sense to make it more anatomically correct, but does it make a difference?

"What you want to have the knee do is be all the way shaped like her knee,” Haas explained. “We need to shape the implants like the natural bones are shaped, and that means shaping the female knee to fit the female anatomy and shaping the male knees to have male anatomy.”

The operation costs between $25,000 and $35,000 - slightly more than the traditional knee replacement. But this procedure is done with tinier instruments, meaning smaller incisions. And that speeds up recovery by about six weeks.

“So how did it go today?” Gupta asked Haas after Upson’s surgery.

“It went great. The implant felt great, it had a great fit,” Haas said. “The ligaments felt really balanced and her knee moved really well.”

If another patient of Dr. Hass's is any indication, she might do more than she could ever imagine. Ten months after her operation, Diane Magnani was back to running and even skydiving.

“My new knee is great,” Magnani said. “I can keep running and do anything I want.”

A few days after surgery, Upson was walking with a cane. She should be about to play catch with her dog, Sadie, in about six weeks.